This invention relates to an improvement of an oil pressure rush adjuster of a directly acting type which is incorporated with an oil pressure unit within a bucket.
A "bottomed" condition herein refers to such a condition that an oil pressure unit is displaced a maximum amount by a cam nose as seen in FIGS. 2 and 9.
A valve actuating mechanism used in an internal combustion engine is subject to influences of wears or thermal expansions, whereby a space or a clearance formed at the valve is deformed during operations and gives bad influences to outputs and makes noises. An oil pressure rush adjuster has been therefore used to rectify the problems caused by the deformed space.
A directly actuating valve mechanism is known which is light in weight with a cam directly striking a shaft end of a valve, and this mechanism has been also employed with the oil pressure rush adjuster as shown in FIG. 8.
The oil pressure rush adjuster is composed of a bucket X and the oil pressure unit Y housed therewithin, and is placed between a cam 300 and the shaft end of a valve 400.
The oil pressure unit Y is slidably mounted on the outer circumference of a cylindrical plunger 101 having an oil hole 104 at its bottom, and comprises a cylindrical body 100 defining a high pressure chamber 102 together with the bottom of the body 100; a spring member 105 provided in the high pressure chamber 102 and biasing the body 100 downward; a check valve 106 disposed in the high pressure chamber for opening and closing the oil hole 104; and a valve spring 107 supporting the check valve 106 and a check valve cage 108 in the high pressure chamber 102.
The oil pressure unit Y is housed in the bucket X, defining a main reservoir 103 as an oil storage between the rear side of a face disc 202 and the hollow portion of the plunger 101 as well as a sub-reservoir 200 communicating, via an overflow recess 203, with the main reservoir 103 partitioned with the circumferential wall of the plunger 101, the sub reservoir 200 being supplied with the actuating oil through an oil feed hole 500 of a cylinder head and an oil hole 510 of the bucket X.
On the other hand, a cam 300 contacts the face disc 202 of the bucket X, while the shaft end of the valve 400 contacts the closed face of the body 100, so that the cam 300 strikes the shaft end of the valve 400 via the oil pressure rush adjuster.
The oil pressure rush adjuster makes use of a rigidity of the actuating oil effected when exerting pressure to the actuating oil filled in the high pressure chamber 102, and the restoring force of the spring member 105 which when releasing the pressure so as to correct the space which has been thermally deformed in the valve actuating mechanism.
A part of the oil to be supplied to the sub-reservoir 200 leaks via a space between the outer circumference of the oil pressure unit Y (the outer circumference of the body 100 in the drawing) and the sleeve 201 forming a partition of the sub-reservoir 200.
If the oil leaks while the engine operates but since the actuating oil is supplied into the sub-reservoir 200 from an oil field hole 500 of a cylinder head and an oil hole 510 of the bucket X, no special problems arise. But once the engine stops, the oil is not supplied from the cylinder head until re-starting the engine. Especially when the engine stops which is furnished with a rush adjuster under an oblique state, sufficient amounts of the oil cannot be secured in the both reservoirs 103, 200 due to the oil leaking. When the engine re-starts, there arises a possibility that air is drawn together with the actuating oil from the reservoir 103 into the high pressure chamber 102.
When the internal combustion engine stops while a cam nose 301 keeps pressing the face disc 202 of the bucket X, the oil pressure unit Y is compressed as shown in FIG. 9, that is, it is most shortened (bottomed condition). If the engine re-starts under this condition, the sliding stroke between the plunger 101 and the body 100 is maximum, and the oil is drawn into the high pressure chamber 102. But since the oil is not supplied thereinto from a cylinder head, as said above while the engine stops, the oil amount is reduced in the main and sub-reservoirs. Therefore air is drawn into the high pressure chamber 102 as much, and the rigidity of the actuating oil which is generated in the chamber 102 is considerably reduced when the plunger 101 is pressed, so that the space of the valve cannot be rectified (the rigidity is changed to be soft, and called as "sponge" condition).